Scientists have been saying for a while that drinking coffee may reduce the chances of acquiring Alzheimer's disease (AD), Parkinson's (PD), and dementia. A new study, published in Frontiers in Neuroscience in October, has taken a closer look into the now popular maxim, analyzing the correlation between Joe and lower incidences of AD.

Their identification of phenylindanes compounds as the source of java's beneficial effect leads to a couple of surprises. First off, decaf is just as effective as caffeinated coffee at avoiding the disease. Secondly, what really matters is how dark the coffee's roast is.

The experiments started much like our days

While the caffeine in coffee is known to produce a short-term increase in alertness, its long-term effect on the brain is less understood, especially since the amount of caffeine in any given cup is dependent on a host of variables. This said, controlled testing has been tricky. Additionally, there are a number of chemicals in java.

Weaver's team was focused on identifying naturally-occurring small molecules that can "inhibit the aggregation of amyloidogenic proteins." That is, proteins whose build up are believed to be a factor in Alzheimer's.

Ultimately, they found that the absence or presence of caffeine made no difference to the aggregation of the toxic proteins. Also ruled out as being of much use were chlorogenic acids — compounds that account for as much as 15 percent of unroasted beans — as well as quinic acid, caffeic acid, and quercetin.

It’s really about the phenylindanes

When coffee beans are roasted, compounds called phenylindanes are generated. The darker the roast, the more phenylindanes are produced. According to the paper, it is these compounds that inhibit the aggregation of the Alzheimer's inducing tau and amyloid-beta proteins. Weaver admits, "So phenylindanes are a dual inhibitor. Very interesting, we were not expecting that."

The takeaway

What all this means is that if developing a neurodegenerative disease, especially Alzheimer's, is a concern, try switching to as dark a roast of coffee, or even espresso, as you find palatable. Caffeinated or not makes no difference in this regard, though the other effects of caffeine are, of course, a whole other issue.

Also, note that there's no indication that drinking coffee does anything to cure Alzheimer's. It simply seems to help avoid acquiring it.